This invention relates to improvements in the invention disclosed in our copending application, Ser. No. 951,460, filed Oct. 16, 1978, for Method And System For Escaping From An Offshore Drilling Platform, the disclosure of which is incorporated by reference herein. There is disclosed in that application an improved system for evacuating personnel in emergency situations, such as a fire, from offshore platforms engaged in hazardous operations involving explosive and combustible fluids, e.g., oil and gas, entrapped in the marine bottom, such as drilling rigs, production platforms, work over platforms, or the like. The system includes a buoyant floating haven anchored in a relatively fixed position near, but at a safe distance from, the platform, a downwardly inclined cableway extending above water from the platform to the haven and a personnel carrier suspended on the cableway for transporting personnel from the platform to the haven.
While the system disclosed in said application is most satisfactory for its intended purpose, improvements are possible and desirable. Thus, the haven shown and described in said application is in the form of a self-propelled vessel, namely, a catamaran. Such a vessel, however, not only is expensive but also subject to some degree of pitching and rolling in rough seas. Further the cableway shown and described in said application is in the form of two parallel cables properly tensioned by appropriate means carried on the haven. While a two-cable cableway provides increased stability for a personnel carrier, it is more expensive than a single cable and, further, it is difficult to maintain the same tension in both cables of a two-cable cableway. Without the same tension, one cable will sag below the other with consequent undesirable leaning of the carrier. Additionally, the provision of means on the haven for tensioning the cableway is unnecessary in most installations because suitable tensioning means usually are readily available on the platform.
While the carrier disclosed in said application is there described as buoyant, the entire system is intended to have the carrier land on the haven. Such a landing requires the cableway lower end to be at a relatively high elevation above water. Such a high elevation requires a relatively large haven in order to provide the necessary support for the lower end of the cableway.